JPS5813441Y2 - Noise reduction circuit for magnetic recording and playback equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a circuit for reducing noise generated by a switch (hereinafter referred to as a recording/playback switch) for switching between a recording state and a playback state of a magnetic recording/playback device.

Generally, when switching the recording/playback switch of a magnetic recording/playback device from the playback side to the recording side, the switch is manually operated directly or indirectly, so the switching speed at this time is not very fast, and pulse noise occurs. The difference is not that big either.

However, when switching from the recording side to the playback side, (this means canceling the normal recording state.

) Since the recording/playback switch uses the force of a coil spring or the like to abruptly switch from recording to playback, it has the disadvantage that the pulse noise generated at this time is extremely large compared to the former.

Also, due to the transient characteristics of the amplifier circuit, large pulse noise causes a delay phenomenon, and is output as noise that is slightly longer in time than the actual pulse width and has middle and low frequency components. There was a defect that appeared on the terminal.

Therefore, in order to completely prevent this type of noise from appearing at the output terminal, it is necessary to completely stop the operation of the amplifier at the same time as the noise occurs.

In order to solve the above-mentioned drawbacks, the present invention is designed to easily set the time during which the operation of the amplifier is stopped without preparing any special circuit elements.

An embodiment of the present invention will be described below with reference to the drawings.

In the figure, 1 is the recording input terminal, 2 is the recording/reproducing amplifier, 3 is the playback output terminal, 4 is the recording/playback magnetic head, 9 is the oscillator for AC bias of the head, and resistor 7 and capacitor 8 are the bias oscillator 9. In order to reduce the ripple voltage contained in the DC power supply, when the operation of the bias oscillator 9 is stopped (when the recording state is released), after stopping the supply of DC voltage,
This is a time constant circuit that is set so that the output of the oscillator 9 gradually decreases due to the discharge current of the capacitor 8, and is provided to prevent the magnetic head 4 from becoming magnetized.

The residual transistor 5 is provided to reduce pulse noise generated when the recording/reproducing switch 10 is switched, and by passing a direct current through the base of this transistor 50, the transistor 5 becomes conductive, so that the operation of the amplifier 2 can be stopped. It is composed of

Switches 10, 11, 12, and 13 are all recording/reproducing switches, and in the operation from playback P to recording R1 and vice versa, all three terminals of the - group of switches are momentarily shorted.
It has a so-called shorting type structure, and the figure shows the playback state.

Note that the resistor 6 limits the base current of the transistor 50.

In the above configuration, the bias oscillator power supply B is connected to the recording side terminal R of the recording/playback switch 10, and the bias oscillator 9 is connected to the neutral (common) terminal via a time constant circuit consisting of a resistor 7 and a capacitor 8. On the other hand, the base of the transistor 50 is connected to the playback side terminal P via the resistor 6, and when the recording/playback switch 10 is switched from playback to recording,
The transistor 5 is turned on only while all the terminals of the switch 10 are short-circuited, and when switching from recording to playback, from the time when all the terminals of the switch 10 are short-circuited,
The structure is such that the transistor 5 is turned on during the period 1 when the capacitor 8 is discharged.

Since the present invention is constructed as described above, it is possible to eliminate pulse noise especially when switching from the recording side to the playback side, and in particular, it is possible to eliminate pulse noise when switching from the recording side to the playback side. This can be easily realized without preparing a dedicated circuit element.

[Brief explanation of the drawing]

The drawing is a circuit configuration diagram of a noise reduction circuit for a magnetic recording/reproducing machine showing an embodiment of the present invention. In the figure, 1...recording input terminal, 2...amplifier, 3...playback output terminal, 4...recording/playback head, 5...・Transistor, 7, 8...
...Time constant circuit consisting of a resistor and a capacitor, 9...
...Bias oscillator, 10-13...Recording/playback switch.

Claims (1)

[Scope of utility model registration request] Connect the recording side terminal of the recording switch to the power supply for the bias oscillator, connect the neutral terminal to the bias oscillator via a time constant circuit, and connect the playback side terminal to the base terminal of the transistor that stops the operation of the recording re-amplifier when it is turned on. When switching the above recording/re-switch from the playback side to the recording side, the above transistor is made conductive only while all terminals of the switch are short-circuited, and when switching from the recording side to the playback side, the above transistor is made conductive. A noise reduction circuit for a magnetic recording/reproducing machine, characterized in that the transistor is made conductive for a period of time during which the time constant circuit discharges from the time when all terminals of the switch are short-circuited.